Hungering and thirst for righteousness, I think the idea of that is that you really have a new desire. This whole process of knowing you have nothing, of repenting, of putting your will under Christ will, then that brings you a whole new desire of life, where before you desired a whole set of things. We all have different desires, some for comfort, some for people to love us and look up to us, some for power and there's all different ways we go about getting that.
Often, people think to follow Christ means starting with your actions and it's, "You know what? When you follow Christ, your actions should change," but the most amazing thing is when the life of Christ comes into you and actually begins to change what you desire. What you desire becomes what Christ desires and that's righteousness. Not just the righteousness of having a life that is righteous before God, because of Christ righteousness, but also the righteousness of living a life before God and men that brings Christ rule to the Earth.